Hifix -> Sound Clips
Hifix sound clips

No HiFix system has operated for a very long time and so far, I have not been able to trace a sound clip. I would be extremely interested to find one. In the mean time, the HiFix transmission can be realistically simulated.

  • HiFix: you are hearing the B slave about 10 dB down on the master, and the C slave about 6 dB down (.wav, 22050Hz/8 bit/mono, 7 seconds, 88 kBytes).
  • HiFix/6: Simulation of a 6-station HiFix/6 chain.
Hyperfix sound clips

Hyperfix chains would naturally sound very different depending on the sequence in use. Some features are distinctive, such as the 'double pip' of the master station.

  • Hyperfix: you are hearing 3 sites in this simulation, which is of a chain running sequences 1-2-1 in mode 3. You can hear the trigger station (very quietly) and slaves 1 and 3. The loudest one (S3) is an exact replica of the Whitby (Hawsker) station. (.wav, 11025Hz/8 bit/mono, 12 seconds, 153 kBytes).

And now for the real ones! Here are some soundclips sent to me by Vaino Lehtoranta:

Vaino's soundclips are most probably of the Swedish chains, which used to be audible in England as well on 2550 kHz.

Deltafix sound clips

The following is a recording of the Seahouses station, on 2834 kHz. The recording was made at Whitby, N. Yorkshire on 23rd October 2006.

  • Deltafix transmission. PSK, encrypted DGPS data. (mp3, 118KB)
Other hyperbolic systems


Now as it happened, David Sparvell G4FTC pointed out to me that there are some sort of transmissions audible on 1810 kHz after dark. David and myself did some work on this signal; we think it's a hyperbolic system very similar in characteristics to HiFix but with some subtle differences- for example, the transmissions are simultaneously on 2 frequencies 815 Hz apart- which could be for lane identification. You can hear two sites quite well with differing fading patterns indicating significantly diffrent locations; and a third can just be heard when the signal is on a peak.

We speculated about the source, as Russia seemed a good bet on two counts- it explains the signal coming up after dark, and its possible they still use MF hyperbolic systems.

I did some trawling on the web and came up with these:

"...there are Russian BRAS and RS-10 navigation systems spreading all over the topband. They sound like a series of dashes.

As these signals are used for hydrographic purposes, they are more active during summer time."

- Vaino Lehtoranta, OH2LX writing on October 1998 on the top band contesting message board. And, from the Spooks Newsletter, another quote from Vaino:

>"...frequency is 3756 kHz with much reduced carrier. It is modulated by tone which spreads up and down symmetrically in about 0.82 kHz steps. Because this is exactly what Bras and Rs-10 transmit, these must have something to do with those systems. A control station? Some people long thought they are time signal stations without knowledge that the transmitted "time period" is not 1 second...." Interesting.

Anyway here's the sound clip- This is the 'beat' between the two of the 820 Hz sidebands, which is resolved on an AM receiver.


Loran is a current wide area navigation system that uses flight-time of narrow pulses on a frequency or 100kHz. The Russian Chayka system is extremely similar and is compatible.

This off-air recording is of a mix of stations audible in the UK

Non-hyperbolic systems


This system, which was known to German people as 'Sonne', was a 'rotating beam' system intended for use over a large area. A beam consisting of two regions, one of morse dots and teh other dashes that overlapped so that in teh centre, a continuous signal was heard. The beam was transmitted from 3 fixed masts but electronically rotated so that a full cycle took about 30 sec. In between cycles, the station ID wa stransmitted in morse from teh centre antenna only, i.e. omnidirectionally. The bearing off was given by counting the dashes until they merged into the equisignal region.

The recording is a simulation of LEC at Stavanger, Norway which remained operational on 319kHz until 1991.

Last Modified 19/05/2009